FENE



FENE stands for the finitely extensible nonlinear elastic model of a long-chained polymer. It simplifies the chain of monomers by connecting a sequence of beads with nonlinear springs. The spring force law is governed by inverse Langevin function or approximated by the Warner's relationship

$$\textbf{F}_i=\frac{H \textbf{R}_i}{1-(R_i/L_{max})^2}$$

Where $$R_i = |\textbf{R}_i|$$ and H is the spring constant.

Total stretching force on ith bead can be written as: $$\textbf{F}_i - \textbf{F}_{i-1}$$.